It runs at 80 MHz, carries 128 KB of Flash and 64 KB of SRAM, and is packaged in a 108-ball BGA.
80 MHz Cortex-M3 — what the speed buys you
The 80 MHz core is the same Cortex-M3 architecture used across the Stellaris 9000 family. That clock rate, paired with the DMA controller and peripheral set, handles a lightweight TCP/IP stack, a CANopen node, and a USB OTG host simultaneously.
The LM3S9781-IBZ80-C5 is officially obsolete. Texas Instruments ended production on the Stellaris ARM Cortex-M3 line. No direct pin-compatible replacement exists within the current TI portfolio.